The orifice plate of the printhead of an ink-jet printer, particularly a thermal ink-jet printer, tends to pick up contaminants, such as paper dust, and the like, during the printing process. Such contaminants adhere to the orifice plate either because of the presence of ink on the printhead, or because of electrostatic charges. In addition, excess dried ink can accumulate around the printhead, particularly if all the ink is not pumped out of the printhead. The accumulation of either ink or other contaminants can impair the quality of the output by interfering with the proper application of ink to the printing medium. In addition, if color pens are used, each printhead may have different nozzles which each expel different colors. If ink accumulates on the orifice plate, mixing of different colored inks can result during use. If colors are mixed on the orifice plate, the quality of the resulting printed product can be affected. For these reasons, it is desirable to clear the printhead orifice plate of such contaminants and ink on a routine basis to prevent the build up thereof. Furthermore, the nozzles of an ink-jet printer can clog, particularly if the pens are left uncapped in an office environment.
Many prior art ink-jet printers use a vacuum pump or the like to prime the printhead, and to remove clogs. However, when color pens are used, a separate pump is required for each set of nozzles of the same color to avoid color mixing. The provision of several separate pumps unduly complicates the mechanism, rendering it more prone to failure, and more expensive.
The clearing of clogged nozzles, and the removal of contaminants, such as paper dust and dried ink from the orifice plate of the printhead nozzle is particularly difficult where a color printhead and a black printhead both are present on the same printhead carriage. In existing wiper systems, such as those described in U.S. Pat. Nos. 4,872,026, and 4,577,203, each wiper blade scrapes each printhead on the printhead carriage. Thus, if one were to have both a black printhead and a color printhead on the same carriage, the same blades would wipe contaminants and dried ink off both printheads. Under these conditions, contamination of the black printhead with colored ink, and of the colored printhead with the black ink is highly likely, thus interfering with the print quality.
Furthermore, existing wiper systems such as those shown in the foregoing patents which utilize only a mechanical wiping action are generally not capable of completely removing dried ink from the orifice plate of a printhead. Dried ink becomes a particular problem with pens which have been in service for a long period of time.
Some of the foregoing problems are overcome by the rotary wiper disclosed in U.S. application Ser. No. 07/463,755, filed on Jan. 12, 1990, and assigned to the Assignee of the present application. However, such a configuration is not always suitable when both black and color printheads are provided in the same carriage, because of the potential for mixing of the inks. Furthermore, although this apparatus is effective in removing most contaminants, old dried ink is difficult to remove even with the foregoing apparatus.
It is, therefore, an object of the present invention to provide a wiper for an ink-jet printer having both a color printhead and a black printhead for removal of contaminants without any mixing of the ink from the two printheads.
It is a further object of the present invention to provide a wiper for an ink-jet printer which includes means for automatically cleaning the wiper as it wipes the orifice plate of the printhead.
It is another object of the present invention to provide a simplified wiper mechanism which is effective in removing paper dust, ink and other contaminants from the printhead orifice plate of an ink-jet printer.
It is another further object of the present invention to provide a wiper for an ink-jet printer which is capable of removing dried ink on the printhead orifice plate.
It is yet another further object of the present invention to provide a method for cleaning the orifice plates of printheads of an ink-jet printer in which there are both a color printhead and black printhead on the same carriage.
It is yet another further object of the present invention to provide a method for cleaning dried ink from the orifice plate of an ink-jet printhead.
It is yet another further object of the present invention to provide a service station for an ink-jet printer which does not require a vacuum pump for cleaning and priming of the printheads.